A high-rolling poker player and Costa del Sol society figure, said to be friends with Princess Diana’s former lover James Hewitt, has gone missing – leaving investors millions of pounds out of pocket.

Nigel Goldman was previously convicted for fraud and jailed in England, writing openly about his crimes in his autobiography, High Stakes: How I Blew £14m, and then set himself up as an investment adviser near Marbella.

But now the flamboyant businessman, who styled himself as a “Sir”, cannot be found by his clients, more than a dozen of whom claim they are owed money after investing in one of his schemes.

Antonio Flores, the lawyer representing Mr Goldman’s clients, said complaints had been made to police in Spain and authorities in the UK. “I think he’s not done anything of what he said he would be doing – invest the money for people,” Mr Flores told The Independent, outlining the allegations. “I think he’s just had a classic vulgar Ponzi scheme, where he just dips in [to the money] whenever he feels like it and pays out clients who shout the loudest.” Mr Flores said Mr Goldman “acted totally outside of any regulation”.

The total amount of money involved could actually be far higher than first thought as typically in cases like this only 25 to 30 per cent of clients come forward, the lawyer said. He said one of Mr Goldman’s clients was missing a “large amount of money”.

According to emails seen by The Independent, a client sent a message to Mr Goldman in November saying: “PLEASE DEPOSIT AS MUCH AS POSSIBLE. The amount you are holding is £500k.”

A reply from an email address used by Mr Goldman said: “Just managed to pay in 425.00 for you – sorry that’s all I can mange [sic] for now, it’s a small start, but more importantly, a gesture of my good intentions for the future.”

Jon Clarke, of The Olive Press, the expat newspaper which broke the story, said he believed the total sum could run into “tens of millions”.

“I would say on the Costa del Sol, Costa del Crime, he was one of the most colourful characters, one of the best-known, and best-loved by some people, a regular at charity events,” he said. “He was charming and definitely funny … but I trusted him about as far as I could throw him.”

Mr Clarke said Mr Goldman was “very good friends” with Mr Hewitt and also claimed to know Sir Mark Thatcher, another leading light of the social scene.

Mr Goldman did not respond to requests for comment on Facebook and to two email addresses he has used. But in a text message published by the Birmingham Mail, Mr Goldman appeared to claim that he himself was a victim of a scam. “It seems some of my brokers turned out to be running a Ponzi scheme with everyone’s money… I did not set out to be a thief,” he said.

Michel Euesden, managing director of Euro Weekly News, where Mr Goldman once worked as a restaurant reviewer, said the businessman had persuaded people he had “gone straight” by saying he had “a pathological fear of returning to jail”. “People have lost their life’s savings,” she wrote. “Here is my personal message to Sir [sic] Nigel… One day soon it will be the last drop of champagne you savour in a very long time.”